Overview of Bladder Outlet Obstruction

In This Article
Table of Contents

Bladder outlet obstruction (BOO) is a problem in which the flow of urine is partially or completely blocked. This produces a number of symptoms, including diminished urination, pelvic pain, and bladder discomfort. BOO can result in complications such as infections and kidney failure. Though the condition can affect males and females, bladder outlet obstruction occurs most often in older men.

The most common issues that can cause this condition include prostate problems, tumors of the bladder, and urethral narrowing. Often, diagnostic testing is necessary to identify the cause of BOO, and medical or surgical treatments can be used to relieve the obstruction.


Typically, bladder outlet obstruction begins with mild, bothersome symptoms that gradually worsen over time. Depending on the severity, the symptoms may be intermittent; you might only experience them once in a while, rather than every time you urinate.

Sometimes, however, a large tumor or infectious abscess may develop rapidly, blocking the bladder outlet and causing sudden effects that are more noticeable and consistent.

Signs of a bladder outlet obstruction include:

  • Difficulty maintaining a forceful urinary flow
  • Stop-and-go flow
  • Reluctance to urinate, also known as hesitancy
  • Terminal dribbling, characterized by slow dribbling of your urine near the end of the stream
  • A strong urge to urinate
  • Pelvic pain
  • Frequently urinating tiny amounts of fluid
  • A feeling of fullness and a sensation of urine remaining in your bladder after you've peed

As the obstruction becomes more severe, you may have to strain your muscles with increasing effort to push urine past the blockage.


Over time, you can develop serious health problems due to bladder outlet obstruction. In fact, neglecting early symptoms may lead to irreversible complications.

Issues that can develop as a consequence of BOO include:

  • Kidney stones
  • Urinary infections (can be recurrent)
  • Urinary incontinence
  • Kidney failure

Prolonged BOO may cause irreversible kidney failure if it is not treated, as the fluid backflows into the ureter and the kidneys.


The bladder is a muscular cavity that holds urine. It is located in the lower abdomen behind the pelvic bone. The urethra is a thin muscular tube through which urine travels from the bladder to the outside of the body. (In men, the urethra is inside the penis. In women, the urethra is shorter and the opening is near the vagina.)

Bladder outlet obstruction is usually caused by physical pressure at the bladder outlet (lower base of the bladder leading to the urethra) or along the urethra.

With BOO, the bladder contracts as usual to initiate the stream of urine, but the outlet is partially blocked.

A number of conditions can lead to bladder outlet obstruction. Medical problems that cause pressure, trauma, inflammation, or scarring of the bladder outlet or the urethra can be to blame.

BOO can develop as a result of:

A mass causing pressure on the bladder outlet can cause mild or severe obstruction, depending on the position and size of the mass. A malignancy doesn't necessarily cause more obstruction than an infection or an enlarged prostate.


Your doctor will start by taking a medical history, asking questions about your urinary symptoms and other health issues such as weight changes, bowel fluctuations, fluid intake, symptoms of sexually transmitted diseases (e.g., itching, burning, pain or discharge in the genital area), and back or pelvic trauma.

Your doctor will look at your abdomen and place light pressure on it to assess for swelling or discomfort. A physical examination can help your medical team spot any visible signs of an STD, such as redness or discharge.

A man with symptoms of BOO may also need to have a prostate examination and a woman may need a pelvic examination.

Labs and Tests

If you have symptoms such as urinary hesitancy or bladder fullness, your medical team may want you to have a number of tests to identify the problem.

Possibilites include:

  • Urine test: Glucose in the urine is a sign of diabetes, blood is a sign of trauma or infection, and bacteria is a sign of infection. Protein and cells may be indicative of cancer.
  • Bladder imaging: A pelvic ultrasound, cystogram, computerized tomography (CT), or magnetic resonance imaging test (MRI) can help your medical team visualize your bladder outlet. This can identify fluid in the bladder, as well as an obstructive mass.
  • Cystoscopy: This test involves the placement of a tube into the urethra and the bladder to visualize the inside of these structures with a camera.

Differential Diagnoses

Diabetes can cause urinary frequency, and it may not be obvious whether your urinary changes are caused by the disease or a bladder outlet obstruction.

Neurological bladder dysfunction can result in a decreased ability to urinate and bladder distension, which may feel similar to the symptoms of BOO.

Diagnostic tests can help distinguish between these causes.


Depending on the cause, you may need interventional treatment for your bladder outlet obstruction. If you have an anatomical issue such as an enlarged prostate or a cancerous tumor, you may need surgery, radiation, and/or chemotherapy to relieve the pressure.

If you have a traumatic injury or scarring, you may need surgical repair so that your bladder outlet can be widened.

Chronic Cases

For persistent problems that cannot be surgically repaired, there are other therapies that can be helpful, including medication and catheterization.

Catheter Placement

If you have a problem with your urethra, such as scarring, you may need to use a catheter—a tube that can be placed in the urethra to pass urine. A catheter can, itself, cause a traumatic injury, so it has to be placed carefully.

Sometimes catheters are kept in place for a period of time, such as during surgery or while in the hospital, or may be used only briefly.


There are medications that can be used to help control urine flow. For example, Flomax (tamsulosin) and others may help with symptoms of urinary retention, but they do not relieve the obstruction.

A Word From Verywell

Bladder outlet obstruction is a serious issue that should not be ignored. It can be effectively managed, however. If you have problems with urination, it is important that you discuss your concerns with your doctor, as bladder problems typically worsen if not treated.

Was this page helpful?
Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Sussman RD, Drain A, Brucker BM. Primary bladder neck obstruction. Rev Urol. 2019;21(2-3):53-62. 

  2. Katsoufis CP. Clinical predictors of chronic kidney disease in congenital lower urinary tract obstruction. Pediatr Nephrol. 2019, June 13. doi.10.1007/s00467-019-04280-0

  3. Reddy SVK, Shaik AB. Non-invasive evaluation of bladder outlet obstruction in benign prostatic hyperplasia: a clinical correlation study. Arab J Urol. 2019;17(4):259-264. doi.10.1080/2090598X.2019.1660071

  4. Lin YH, Hou CP, Juang HH, et al. Association between bladder outlet obstruction and bladder cancer in patients with aging male. J Clin Med. 2019;8(10). doi.10.3390/jcm8101550

  5. Gravas S, Kyriazis I, Klausner AP. Lower urinary tract symptoms including bladder outlet obstruction: What's new in diagnostics?. Eur Urol Focus. 2018;4(1):14-16. doi.10.1016/j.euf.2018.04.004

  6. Vouri SM, Strope SA, Olsen MA, Xian H, Schootman M. Antimuscarinic use in men treated with bladder outlet obstruction medication therapy. Urology. 2018;122:76-82.doi.10.1016/j.urology.2018.08.039

Additional Reading